• eft
• massive charged spin 2
• positivty bounds
• Velo-Zwanziger

Massive charged high-spin particles do exist in nature. Examples are the QCD resonances pi_2 (1670) and rho_3(1690).
In QCD high-spin resonances arise as relativistic, strongly-coupled bound states of quarks and gluons, with masses comparable to or larger than their inverse typical size, which is set by the interaction scale. In the language of Effective Field Theory (EFT), this implies that the cutoff is of the order of the high-spin state mass.
This raises the question whether it is possible at all to describe a consistent EFT for a massive high-spin particle with a parametric separation from the mass. While the answer appears to be negative for s>2, in this thesis, we focus on the case of a spin-2 particle coupled to electromagnetism with charge q.
It is well known that massive charged fields with spin greater than 1 exhibit various pathological features such as the so-called Velo-Zwanziger acausality, where modes propagate superluminally around a constant electromagnetic background, or the number of propagating degrees of freedom may differ from that of the free theory, rendering the system unstable.
The aim of this thesis is to revisit these pathologies from a different perspective to determine if a consistent EFT for a massive charged spin-2 particle can exist. Indeed, it was observed that a consistent EFT with a Lorentz invariant, unitary, casual and local UV completion, requires the positivity of certain Wilson coefficients as a consequence of the analytic properties of the S-matrix